Distribution header for air conveyor

ABSTRACT

An improved conveyor tube and distribution header for air conveyors such as air seeders serves to distribute seed and/or fertiliser products from the aircart to individual delivery tools via pneumatic conveyor tubes. The apparatus is adapted to achieve substantially even distribution of the materials being conveyed to each of the delivery tools. The apparatus includes a conveyor tube for conveying air-entrained material from a first location to a distribution head, which conveyor tube has an interior surface with a plurality of inwardly directed spaced apart projections which are disposed in spaced annular rows extending around the lengthwise axis of the tube for creating controlled turbulence in the flow of material. These projections are arranged in a particular manner to achieve the desired degree of turbulence. The distribution head has a flow inlet for receiving the air-entrained material from the conveyor tube and the head includes angularly spaced apart outlet ports and a flow divider device for dividing the incoming flow into generally equal parts and directing the divided portions of flow outwardly through the outlet ports. The flow divider includes a flow deflector disposed within a flow dividing chamber which deflector has flow confining ridges separated by smoothly contoured valleys arranged to divide and direct the flow in a smooth and efficient manner.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. application Ser.No. 09/244,667, filed Feb. 4, 1999. The entirety of that parentapplication is incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates to improved apparatus for the delivery ofparticulate material, which apparatus is specially adapted for use withan agricultural pneumatic conveyance device such as an air seeder.

BACKGROUND OF THE INVENTION

Seed and fertiliser products are distributed from a hopper or aircart toa delivery tool via a pneumatic conveyor tube. The travel path isinitially substantially lateral over the first part of the distance fromthe supply hopper to the delivery tool. Then, the conveyor tube isprovided with a substantially vertical orientation and its upper endconnects with a flow dividing header. The header directs theair-entrained product into a number of conduits connected with theground openers and delivery tools. In some cases the conduits of theheader communicate with secondary headers before distributing theproduct to individual delivery tools. It is important to achieve an evendistribution of product to each conduit from the header to apply equalamounts of product in each furrow. An uneven distribution results ininefficient soil and fertiliser usage, and affects the uniformity of theproduce growth. A term commonly used is the coefficient of variation(CV) which is a measure of the uniformity of distribution across thedistribution apparatus. A CV of 15% or greater is deemed unacceptable. ACV below 5% is considered very good.

The variation in distribution is effected by a number of factors. Forinstance, grain travelling in the conveyor tube tends to travel alongthe inside surface, particularly following any bend for redirection tovertical. The outlet of the conveyor tube delivers the material to aspreader in the distribution header which separates the material intochannels arranged circumferentially about the header. Thus, if theproduct material is more heavily concentrated at one side of theconveyor tube, distribution will not be even. To deliver the productmore evenly into the header, a number of designs have been proposed tocreate turbulence in the conveyor tube forcing the product away from theinside surface, and to centre the stream of product entering the header.

U.S. Pat. No. 4,717,289 issued to S. Popowich in 1988 discloses acorrugated delivery tube for use with a horizontal distribution head.Corrugations tend to direct material from the side walls in asubstantially horizontal system with gravity also affecting the stream.In a substantially vertical orientation, many materials may follow thecorrugated surface without experiencing enough turbulence to achieve thedesired result.

A vertical header system allows a larger number of separation channelsto be arranged circumferentially, without constricting the size of thechannels which constriction would increase the pressure requirements andpotentially cause more damage to the seed.

Canadian Application No. 2,111,611 to G. Bourgault published in June1995 discloses the use of a central baffle to divide the material intotwo streams as it is redirected through a 90 degree bend and centeringdeflector rings. This is a relatively complicated structure tomanufacture. Further, the seed and other material is exposed to aplurality of deflecting surfaces and since they are travelling at highspeed this increases the possibility of damaging the seed in particular.

The use of a dimpled distribution tube is disclosed in Canadian Patent1,167,704 issued to D. Kelm in 1984. A regular pattern of dimples, orinterior projections, creates turbulence within the material flow. Thisdesign includes a number of variations in an attempt to improve theuniformity of distribution. Both cylindrical and conical tube sectionsare disclosed having regularly spaced dimples. An alternative embodimentplaces a dimpled section between two 45 degree bend sections to act onthe material more gradually. This design improves the distribution ofmaterial considerably over the previous designs. However, the CV resultsof the Kelm device are somewhat inconsistent depending on the productused and the rate of delivery.

Various product materials, e.g. peas, wheat, canola and fertilisersexhibit different responses to turbulent flow. The objective is toprovide a uniform stream of material to the dividing spreader of theheader. Since any number and combination of materials may be distributedby the same equipment, it is desirable to find an optimised mediansystem suitable for the full range of products to provide the necessaryversatility.

Kelm identified that changing the placement of the dimpled tube sectionwithin the conveying system has an effect on the CV from thedistribution head. However, it is not practical to reconfigure theconveying system for different products or application conditions.

The distribution head design also has a substantial effect on the CV.The prior art has provided a wide variety of distribution heads. Someheads promote turbulence in the flow while others make attempts toreduce turbulence in the head. Reference may be had to Kelm CA1,097,149; Weiste AU 437,160; EP 211,295; Wurth SU 1,496,668; GillespieU.S. 3,189,230; Oberg et al U.S. Pat. No. 4,191,500; Smith et al4,413,935; Widmer et al U.S. Pat. No. 4,562,968 and Memory CA2,073,237-A among others. Although several of these designs werepartially successful it is the opinion of those skilled in this fieldthat there is room for improvement insofar as effect on CV is concerned.

SUMMARY OF THE INVENTION

It is an objective to provide improved conveyor tubes and distributionheads for producing more even product distribution despite changingvariables including product size, shape, density and mixture.

The present invention in one aspect relates generally to a conveyor tubefor use in a distribution system for conveying air-entrained materialbetween a first location to a distribution head, which has an interiorsurface with a plurality of inwardly directed spaced apart projections,said projections forming a plurality of spaced annular rows which extendaround a lengthwise axis of the tube for creating controlled turbulencein the flow of material.

According to one feature of the invention, the space between at leastsome of the annular rows of projections decreases from one end towardanother end of the conveyor tube.

According to another aspect of the invention the space between saidannular rows of projections decreases in the direction of flow of thematerial through the conveyor tube from an inlet portion to an outletportion thereof. Stated differently, annular rows nearer an end of theconveyor tube which is closest to the distribution head, when in use,are preferably more closely spaced than the rows closest to the firstlocation. This helps provide adequate turbulence and acceptable CVs fora wide range of products.

According to another preferred feature the projections forming theplurality of annular rows may be arranged such that projections formingone row are angularly offset about the lengthwise axis of the tube withrespect to the projections of an adjacent row. This helps to ensure thatall particles of the material being conveyed are subjected toturbulence.

The conveyor tube advantageously includes a straight section of uniformdiameter adapted to be vertically positioned when in use and having saidrows of projections formed therein, said projections being of uniformdepth and having their inner extremities concentrically positioned aboutthe central lengthwise axis of the tube.

Further preferred features include a smoothly curved elbow sectionleading into an inlet portion of said straight section with saidstraight section having a first space devoid of projections between theelbow section and a first row of said projections at said inlet portionand a second space devoid of projections between the last row of saidprojections and an outlet end of the straight section.

Preferably said second space is not less than about 2 to 3 inches long,the total length of said straight section preferably being about 12 to16 inches.

Advantageously said elbow section has a bend angle not greater thanabout 75 but the bend angle can vary between 70 degrees and 90 degrees.

The inwardly directed extremities of said projections in one preferredembodiment lie in a base circle having a nominal diameter ofapproximately 2 inches. Stated more accurately the diameter of said basecircle may be about

1.97 to 2.0 inches, said tube having a nominal diameter of about 2.5inches.

Typically said projections are of a semi-spherical or bulbous shape and4 to 8 rows of said projections may be provided. Said projections arealso typically arrayed in columns, there being 8 to 12 columns spacedequally around the circumference of the conveyor tube. In a preferredembodiment there are 6 rows and 12 columns of said projections.

A distribution system for conveying air-entrained material in accordancewith another aspect of the invention comprises an improved distributionhead which is well-suited for use with the conveyor tube as describedabove. This distribution head has a flow inlet for receiving theair-entrained material from said conveyor tube, a plurality of angularlyspaced apart outlet ports and flow divider means for dividing theincoming flow into generally equal parts and directing the dividedportions of the flow outwardly through the respective outlet ports. Theflow divider means may include a flow divider chamber defined withinsaid distribution head and a flow deflector disposed within said chamberand having flow confining ridges thereon separated by smoothly contouredvalleys each associated with a respective one of said outlet ports.

The distribution head in the preferred embodiment defines a central axiswith said flow inlet being aligned with and concentric with said centralaxis and said outlet ports being in said angularly spaced apart relationand extending radially outwardly from said central axis, said flowdeflector having a nose centered on said central axis and said flowconfining ridges commencing downstream of said nose and curvinggradually around from combined axial and radial directions adjacent saidnose into generally radial directions while the contoured valleysbetween said ridges gradually become deeper to ultimately merge withinterior surfaces of the outlet ports.

The outlet ports preferably are of circular cross-section and areequally angularly spaced about said central axis with said outlet portsextending normal to said central axis and lying in a common plane.

The distribution head advantageously may include three main sectionsnamely, a bottom section having said inlet therein and having firstrecesses defining the bottom halves of said ports, a top section adaptedto matingly engage said bottom section and having second recessescomplementing said first recesses to define said outlet ports, and aninsert section defining said flow deflector adapted to seat in said topand bottom sections with said nose portion directed toward said flowinlet and axially aligned therewith.

Preferably said flow inlet tapers inwardly in the flow direction toaccelerate and centre the flow before it meets the flow deflector.

Further features of the invention will become apparent from thefollowing description of preferred embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation view of the conveyor tube in accordance witha preferred embodiment of the invention and having a distribution head,also in accordance with a preferred embodiment of the invention, mountedat the upper end of the conveyor tube;

FIG. 2 is a longitudinal section of the conveyor tube and distributionhead of FIG. 1 shown in perspective;

FIG. 3 is a section view of the conveyor tube taken along line 3—3 ofFIG. 1 and illustrating the manner in which adjacent rows of projectionsare angularly offset relative to one another;

FIG. 4 is a further somewhat diagrammatic side elevation view of theconveyor tube wherein several variables affecting the performance havebeen identified;

FIG. 5 is an exploded view of the distribution head showing the top lid,flow deflector insert, and the top and bottom sections of the head;

FIG. 6 is a further exploded view of the distribution head but with theseveral components of same shown in the perspective;

FIG. 7 is a view of the distribution head and conveyor tube in sectionwith the section plane extending along the axis of an opposed pair ofoutlet ports and lying in the vertical central axis of the distributionhead;

FIGS. 8A is a perspective view of the lower surface of the bottomsection of the distribution head;

FIG. 8B is a bottom plan view of the top section of the distributionhead;

FIG. 9 is a perspective view of the lower surfaces of the flow deflectorinsert illustrating the shape of the flow confining ridges and contouredvalleys between the ridges;

FIGS. 10, 11 and 12 are bottom plan, side elevation and top plan viewsrespectively of the flow deflecting insert illustrated in FIG. 9;

FIGS. 13, 14 and 15 are perspective, end elevation and side elevationviews of the nose of the flow deflector insert; and

FIG. 16 is a table of design data and test results referred to below asTable II.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring firstly to FIGS. 1 and 2 there is shown an upright conveyortube 10 having a distribution head 12 mounted to the upper end of same.As described in the above-noted patent to Kelm, for example, the loweror inlet end 14 of the conveyor tube receives air-entrained granularmaterial such as seed and/or fertiliser by way of a blower and meteringdevices (both not shown) mounted on an air cart in a manner well knownin the art. As this air-entrained material passes upwardly through theconveyor tube 10, inwardly directed and spaced apart projections 16disposed in the vertical section of the conveyor tube, and which will bedescribed in full detail hereinafter, serve to impart a controlleddegree of turbulence in the upwardly moving flow, which flow then passesinto the distribution head 12.

The distribution head 12 is designed to swing the flow from the verticaldirection around into horizontal directions and to divide the flow thusreceived substantially equally among the several outlet ports 18 whichextend radially outwardly from the distribution head in equallyangularly spaced relationship to each other. These outlet ports 18 areconnected to flexible hoses (not shown) secured to ports 18 by clamps20, each of which hoses leads to a respective delivery tool. Anysecondary header may be of similar construction as distribution head 12and may employ a conveyor tube essentially the same as conveyor tube 10.It is also noted that the novel head 12 and tube 10 may be employed inthe primary and/or any secondary distribution system as required toachieve the desired results.) As noted previously, it is of importancethat the delivery tools across the width of the machine receivesubstantially equal flows of product material so as to achieve acoefficient of variation (CV) of substantially less than 15% andpreferably a CV not greater than about 5%.

Distribution Head

Referring now to FIGS. 5-12, the multi-port distribution head is shownin detail. The distribution header is symmetrical about its centralvertical axis designated X-X. As best seen in FIGS. 5 and 6, thedistribution head 12 comprises four main parts namely, a top cover 22, aflow deflecting insert 24, a top section 26 and a bottom section 28.

The top and bottom sections 26, 28 as well as the flow deflector 24 arepreferably moulded from a polyurethane glass filled plastics material,which material resists wear due to abrasion resulting from the materialsbeing handled and which at the same time provides for economy in themanufacturing processes.

The distribution head 12 is provided with a centrally located flow inletspigot 30 which is snugly received in the upper end of the conveyor tube10 (FIGS. 2 and 7). Radial flange 31 fixed to the upper end of conveyortube 10 is provided with spaced apertures through which fasteners 33extend into head 12 to secure the latter in position on the upper end oftube 10. The inlet spigot 30 is integrally formed with the bottomsection 28 of the head. The top and bottom sections 26, 28 of the headtogether define the above-noted plurality of radially outwardlyprojecting outlet ports 18 with said outlet ports extending in equallyangularly spaced relationship to each other all around the verticalcentral axis of symmetry X-X of the distribution head 12 and with theoutlet end portions of said ports all lying in a common plane normal tosaid central axis X-X.

The friction of the flow divider insert 24 is to divide the incomingflow received via the flow inlet 30 into substantially equal parts whiledirecting the divided portions of the flow outwardly through therespective outlet ports 18. Accordingly, the distribution head 12includes a flow divider chamber 32 (FIG. 7) defined within thedistribution head 12 with the above-noted flow deflector insert 24 beingseated within the top section 26 of the head. The flow deflector 24(FIGS. 9-12) is provided with a downwardly directed nose 34 accuratelycentered on the vertical central axis X-X of the distribution head. Flowdeflector 24 is also provided with a plurality of radially arranged flowconfining ridges 36 separated by smoothly contoured valleys 38 each ofwhich is associated with a respective one of the outlet ports 18. Ingreater detail, the flow confining ridges 36 commence immediatelydownstream of the nose 34, initially being very shallow, with saidridges 36 thence curving gradually around from combined radial and axialdirections adjacent the nose 34 into generally radial directions whilethe contoured valleys 38 between the ridges gradually become deeper suchthat these valleys in the flow deflector insert 24 ultimately coincideor match up with the interior surfaces of the outlet port portions 18_defined by the top section 26 of the head.

The bottom section 28 of the head 12 is also provided, immediatelydownstream of the flow inlet spigot 30, with a plurality of shallowconcave transition surfaces 40 each of which leads from the inlet spigotinto a respective one of the radially disposed outlet port portions 18_as defined in said bottom section 28. Additionally, the interior surface42 of the flow inlet spigot 30 gradually tapers inwardly in thedirection of the flow to accelerate and centre the flow before it meetsthe flow deflector insert 24. All of these features serve to ensure thatthe upwardly moving flow entering via the flow inlet spigot 30 is wellcentered on the central axis which helps ensure the flow is divided intoequal parts and is at the same time smoothly swung around from avertical direction into substantially horizontal directions and passedin generally equal parts with a minimum of flow restriction outwardlythrough the respective outlet ports 18.

Generally speaking air flow velocities within the conveyor tube 10 andthe distribution header 12 are conventional, i.e. within the rangepersons skilled in this art would normally use for comparable prior artequipment.

For good results it is important to ensure that the three main sections24, 26, 28 of the distribution head 12 are accurately fitted together.With reference to FIGS. 5 and 6, for example, it will be noted that thebottom section 28 is provided with a plurality of conical projections 44disposed in radially spaced apart relationship and each adapted to enterinto a correspondingly shaped recess 46 located in the top section 26 ofthe header. In addition, in order to ensure accurate positioning of theflow deflector insert 24, the outer perimeter of the insert is providedwith an outwardly projecting annular ledge 48. This ledge 48 is snuglyreceived in a shallow annular step-like recess 50 provided in the topsection 26 of the head 12. This ensures that the flow deflector 24 isaccurately centered within the top section 26.

Furthermore, to ensure that the flow deflector 24 is accuratelypositioned angularly, the step-like recess 50 in the top section isprovided with angularly spaced apart semi-circular tabs 52 whichco-operate with correspondingly sized semi-circular notches 54 providedin the outwardly projecting flange 48 of the flow deflector 24.Fasteners (not shown) extending through aligned apertures 51, 53 in thetop and bottom sections 26, 28 serve to secure these sections together.Flow deflector insert 24 is held in place by the top cover 22 which, inturn, is secured by spaced apart spring clips 55 (FIGS. 2 and 7) ofsuitable design.

Reference will now be had to the nose 34 of the flow deflector which wasbriefly referred to above. This nose 34 is shown in detail in FIGS. 13to 15. The nose 34 has an elongated cylindrical stem 60 which fitssnugly into a central bore 62 defined in the flow divider insert. Atransverse aperture 64 is provided in the distal end of the stem 60 toreceive a pin to retain the nose in the flow deflector 24. The nose 34is provided with an annular shoulder 68 which abuts up against a narrowannular radially directed surface 70 surrounding the central bore 62 ofthe flow deflector. The nose 34 is of a generally truncated conicalshape with the extreme proximal end 72 of the nose being flat adjacentits central longitudinal axis with such flat portion thence merging withthe conical wall 74 of the nose via an arcuately curved annulartransition portion 76.

The nose 34 should be made of a relatively hard long wearing materialthereby to resist abrasion and wear created by the incoming particulatematerial which of course impinges heavily on the nose 34 duringoperation. It is of course important that the nose 34 be absolutelysymmetrical all about the central axis X-X of the distribution head 12since any deviation from symmetry will adversely affect the flowdivision process.

While the distribution head shown in the drawings is provided with tenoutlet ports 18, it should of course be realised that the number ofoutlet ports 18 can be varied depending upon the circumstances. Commonlyused distribution head embodiments employ anywhere from seven to twelveequally angularly spaced outlet ports which are sized to ensure that theflow velocity outwardly of each outlet port is sufficient as to ensurecontinued entrainment of the materials being conveyed thus assisting inavoiding clogging problems.

The following table provides some typical dimensions for thedistribution head, such dimensions being for illustrative purposes onlyand not for purposes of limitation.

TABLE I (see FIG. 7) D1 - head diameter 7.5 inches d - radial port innerdiameter 1.5 inches D2 - flow inlet inner diameter 2.5 inches T - flowdeflector top to nose tip distance 1.625 inches N - number of outletports 7 to 14

Conveyor Tube

The upright conveyor tube 10 referred to previously in connection withFIG. 1 will now be described in detail.

As noted previously, the lower or inlet end 14 of the conveyor tubereceives the air entrained granular material from the aircart and as theair entrained material passes upwardly through the conveyor tube 10, themultiplicity of inwardly directed and spaced apart projections 16disposed in the vertical section of the conveyor tube impart acontrolled degree of turbulence in the upwardly moving flow, whichturbulent flow then passes into the distribution head 12 which acts onthe flow in the manner described previously.

As shown in the drawings, FIGS. 1-4, the tube 10 includes a straightsection 80 of uniform diameter which is vertically positioned when inuse and which has a multiplicity of inwardly directed spaced apartprojections 16. These projections 16 form a plurality of spaced annularrows 82, which rows extend around the lengthwise central axis of thetube. The space between at least some of the annular rows 82 decreasesin the direction of material travel through the tube 10, i.e. in thedirection of flow through the tube from the inlet portion to the outletportion thereof. As shown in the drawings, annular rows 82 ofprojections 16 which are closest to the distribution head 12 are moreclosely spaced than rows nearer to the tube inlet.

For a 2½ inch outside diameter tube with 6 rows of dimples, the spacingsstarting at the bottom row could be, for example, 2¼, 2, 1½, 1½, 1½inches, i.e. the smallest spacing are near the outlet end.

The inwardly directed projections 16 are preferably formed by way of“dimples” which are made in the wall of the tube 10 from the exterior,with the relatively thin-wall tube being deformed inwardly to form thecorresponding projections 16. The dimples may be made with a round nosepunch such that the projections have a semi-spherical or bulbous shape.

It should also be noted that the projections 16 forming the plurality ofannular rows 82 are arranged such that projections forming any one roware angularly offset by a selected angle A (FIG. 3) about the lengthwiseaxis of the tube with respect to the projections 16 of an adjacent row.This ensures that all of the material being conveyed is subjected to ameasure of turbulence, particularly material which might otherwise tendto travel closely along an interior surface of the tube.

It will be noted that the lower or inlet end portion 14 of the conveyortube 10 includes a smoothly curved elbow section 84 leading into theinlet portion of the straight section. The curved elbow section maysubtend an angle from about 70 degrees to about 90 degrees although withan increasing angle there is a greater tendency for the material to moveaway from the center of the tube under the influence of centrifugalforce and to follow along the inside wall of the tube 10. Accordingly,this angle should be kept as small as conveniently possible andpreferably not greater than about 75.

Another feature of the conveyor tube 10 is that the above-noted straightsection 80 has a first space 86 devoid of projections between the elbowsection and the first row of projections at the inlet portion and asecond space 88 devoid of projections between the last row ofprojections and the outlet end of the straight section, i.e. the endwherein the inlet spigot of the distribution header is fitted.

A substantial number of tests have been carried out and the results ofthese tests are set out in Table II which appears as FIG. 16. Some ofthe variables which are of importance are briefly discussed below.

1. Variable Row Spacing

The varied row spacing has been discussed above. It was found that forconstant row spacing, i.e. the row spacing between any two rows beingthe same, there was an optimum CV value for each product tested.However, to ensure that the conveyor tube 10 worked acceptably well forall products the row spacing was varied as described above and asfurther noted in the tables. By varying the row spacing an acceptable CVwas provided for virtually all products which one might desire to use.

2. Uniform Projection Depth With Projections Concentrically PositionedWithin the Tube

Experiments have revealed that the projections 16 (and the dimples whichform them) should be concentric within the tube 10. In one preferredembodiment of the invention the inwardly directed extremities of theprojections lie in a base circle having a nominal diameter of about twoinches, this base circle of course being centered with the verticalcentral axis of the straight portion 80 of the tube. This is based on atube nominal outside diameter of 2.5 inches, the tube wall being of 16gauge thickness steel. Stated more accurately for this example, it isdesirable that the base circle diameter be 2.00 inches +0, minus 0.030(giving a tolerance range of 1.97 inches to 2.00 inches for thisparticular example). A range of tube diameters to cover this desiredclearance is from about 2.25 to 2.75 inches. It does not appear thattube diameters outside this range will be accepted by the industry.

3. The Top Space is Also of Significance

A top space of less than 2 inches appears to be detrimental while 2.5inches appears to be optimal for most products. This short length ofspace free of projections appears to give the product being conveyed ashort period of time to “even out” before it encounters the distributionhead 12. (The bottom space is less important but should be less thanabout 2{fraction (1/2+L )} inches.)

4. The Number Of Annular Rows Of Projections is Also of Some Consequence

For a conveyor tube as described having a nominal diameter of about 2.5inches 4 to 8 rows of projections could be used but 6 rows ofprojections are found to work best to allow an acceptable compromise inCV's for all reasonable products.

5. The Number Of Columns of Projections is Also of Some Consequence

The columns of projections 16 extend in the lengthwise directions of thetubes and the number of columns in the 2.5 inch tube was varied between8 and 12. Twelve columns of projections provided the most acceptablecompromise for all products.

6. Elbow Bend Angle

The elbow bend angle range has been discussed above and while it can bevaried between 70 and 90 degrees, the lower the bend angle the better,with the most acceptable compromise in the CVs being at bend angles notgreater than about 75.

The results of extensive tests carried out on various designs of aconveyor tube and the effect on the CVs for various products beingconveyed are set out in Table II in some detail. Reference may be had toFIG. 4 for an understanding of the various terms used. Note also theterm “dimple” is used in place of the term “projection” in the table, itbeing understood that they have the same meaning. All of these testswere conducted utilising distribution heads conforming substantially tothat described herein. It would be possible to use the conveyor tubewith other forms of distribution head but CVs inferior to those shown inthe tests could be expected since it is important that the distributionhead be capable of functioning in an efficient manner and thedistribution head described above has been designed such that it worksbest with conveyor tubes of the type described herein. In other words,while it is believed that both the conveyor tube as described and thedistribution head as described will work reasonably well with othercomparable equipment, it is the combination of the two which providesthe best results.

With further reference to Table II the tests conducted on the “dimpled”tubes 10 were progressive in nature. One set of tests was used todetermine the ideal values for a certain variable at a time. It shouldbe noted that the data tables presented are only representative of thehundreds of tests conducted. It should be noted that the applicationrate (lb/acre) of the product being tested affects the CV. Onlyidentical products with similar application rates can be compared withone another.

Most of the comparisons are made to analyse the effects of the variableson a variety of products. While all products are important, it should benoted that canola and fertiliser represent opposite ends of the spectrumof product characteristics.

The fixed criteria of the tube essentially were the elbow angle, offset,dimple tube height and diameter.

If the results from test QA are compared with those of test RA, it isseen that canola prefers a narrower dimple spacing while wheat prefers awider spacing. The results also indicate that canola prefers a large topspace and wheat prefers a large bottom space.

Generally, it can be said that canola and high rate fertilisers preferan aggressive pattern. Wheat seems to prefer a less aggressive pattern.Therefore, it was decided to use only 6 rows at a {fraction (3/16)}dimple depth. The pattern becomes less aggressive and allows more spaceto be allocated to the top and bottom spaces. The results of test PGconfirm this.

The PG test results also reveal something further. Although the dimplepattern is quite aggressive and has a large top space, canola CV's arestill quite high. This shows that there is a limit to the ideal topspace for canola. A top space of smaller than 2Δ or larger than 3Δ willproduce adverse effects on canola.

Using the varying row spacing (see “Design” T1 and T6) allows for therequirements all products tested to be met in order to produceacceptable CV's. The less aggressive wide spaced rows of dimples at thebottom are more suited for wheat; the more aggressive closer row spacingat the top is better for canola.

The ultimate goal was to find a pattern that produced acceptable CV'sfor all range of products. Therefore, the final preferred design settledon (see the test headed “Design”) is the best compromise between all theproducts.

It will be understood that changes in the details, materials, steps andarrangements of parts which have been described and illustrated toexplain the nature of the invention will occur to and may be made bythose skilled in the art upon a reading of this disclosure within theprinciples and scope of the invention. The foregoing descriptionillustrates the preferred embodiment of the invention; however,concepts, as based upon the description, may be employed in otherembodiments without departing from the scope of the invention.Accordingly, the following claims are intended to protect the inventionbroadly as well as in the specific form shown.

Having thus described the invention, what is claimed is:
 1. Adistribution head which conveys air-entrained material received from anupright conveyor tube, for use in a system said distribution head havinga flow inlet for receiving the air-entrained material from said conveyortube, a plurality of angularly spaced apart outlet ports and flowdivider means for dividing the incoming flow into generally equal partsand directing the divided portions of the flow outwardly through therespective outlet ports, said distribution head having a central axiswith said flow inlet being aligned with and concentric with said centralaxis and said outlet ports being in said angularly spaced apart relationand extending radially outwardly from said central axis, said flowdivider means including a flow divider chamber defined within saiddistribution head and a flow deflector disposed within said chamber andhaving flow confining ridges thereon separated by smoothly contouredvalleys each associated with a respective one of said outlet ports, saidflow deflector having a nose portion centered on said central axis andsaid flow confining ridges commencing downstream of said nose andcurving gradually around from combined axial and radial directionsadjacent said nose into generally radial directions while the contouredvalleys between said ridges gradually become deeper into said deflectorto ultimately meet smoothly with interior surfaces of the outlet ports.2. The distribution head of claim 1 wherein said outlet ports are ofcircular cross-section and are equally angularly spaced about saidcentral axis with said outlet ports extending normal to said centralaxis and lying in a common plane.
 3. The distribution head of claim 2comprising three main sections, namely, a bottom section having saidflow inlet therein and having first recesses defining the bottom halvesof said ports, a top section adapted to matingly engage said bottomsection and having second recesses complementing said first recesses todefine said outlet ports, and an insert section defining said flowdeflector adapted to seat in one of said sections with said nose portiondirected toward said flow inlet and axially aligned therewith.
 4. Thedistribution head of claim 3 wherein said flow inlet tapers inwardly inthe flow direction to accelerate and centre the flow before it meets theflow deflector.
 5. The distribution head of claim 3 wherein the bottomsection of the distribution head has a plurality of shallow concavetransition surfaces each leading from said flow inlet into a respectiveone of said recesses defining the bottom halves of said ports.
 6. Thedistribution head of claim 5 wherein said flow inlet tapers inwardly inthe flow direction to accelerate and centre the flow before it meets theflow deflector.